This invention relates to zeolites as ingredients to provide warming in personal care products in the form of lotions, ointments, creams and the like. More particularly, this invention involves Zeolite A that has been treated to substantially reduce adsorption of gases.
Personal care products are often solutions, suspensions or emulsions of various ingredients in appropriate vehicles to provide lotions, ointments and creams of the proper rheology to be applied. These products include toothpastes, facial creams, medicated creams, cleansing creams, analgesic balms, cosmetic lotions and the like. Zeolites have been included as ingredients in personal care products such as toothpastes (U.S. Pat. Nos. 4,349,533; 4,159,316; 4,187,287 and 3,250,680), cleansing and medicated creams (U.S. Pat. Nos. 4,362,715 and 3,250,680), analgesic balms (U.S. Pat. No. 4,379,143) and others. In these products the zeolites function as abrasives, astringents, carriers, deodorants and as sources of heat for self-warming products.
The self-warming products require that the zeolite be activated so that it releases heat upon adsorbing water when applied. A problem that has been found when activated zeolites have been tried in such formulations is swelling upon aging or other environmental factors. This swelling, which can bulge and burst the container as well as changing the texture of the product, is caused by degassing of the zeolite (see U.S. Pat. No. 4,159,316). Activated zeolites readily adsorb non-polar gases, particularly nitrogen. When the gases are replaced in the zeolite by some other constituent, or by a change in temperature, swelling results. Some products can be formulated so that none of the ingredients will replace the gas. This expedient does not prevent degassing because of environmental factors, and severely limits the materials available in formulating the desired product. Heating the partial or completed composition can remove the gas, but there is a risk in changing the ingredients. A better solution would be to provide a zeolite that does not adsorb nitrogen.
Several investigators have found that Zeolite A in the potassium form does not adsorb nitrogen or oxygen (see page 113 of Peterson's "Influence of Presorbed Water on the Sorption of Nitrogen at Ambient Temperatures," ACS Symposium Series 135, American Chemical Society, Washington, DC, 1980). Such potassium form zeolites have been used in adsorbent combinations for sealed thermal windows (see U.S. Pat. Nos. 4,151,690 and 4,141,186).
It is an object of this invention to provide a form of Zeolite A that contains both sodium and potassium, in such a manner that the zeolite does not adsorb gases and has a high heat release on hydration and is suitable for personal care products. It is a further object of this invention to provide a Zeolite A that contains sodium and potassium in such a manner that the zeolite can be pH-adjusted while maintaining a high heat release upon hydration. Such pH-adjusted materials are often required for personal care products.
The prior art patents usually indicate the sodium form of Zeolite A as useful in these warming compositions. It is well recognized that Zeolite A can be treated so that it contains various metals such as calcium and the like. Such materials also sorb and desorb gases in an undesirable manner. It is a further object of this invention to provide a Zeolite A that may contain sodium and other metals with potassium so that the zeolite does not sorb gases and has a high heat release when moistened.